First find of polycrystalline diamond in ultrahigh‐pressure metamorphic terrane of Erzgebirge, Germany

摘要: This article describes polycrystalline diamond from the Erzgebirge ultrahigh-pressure metamorphic (UHPM) terrane of Bohemian massif related to Variscan (340 Ma) continent-continent collision. The foils included in zircon were prepared with focused ion beam (FIB) and studied transmission electron microscopy (TEM). Each domain consisted a series monocrystals (from 1 4 up 15) containing numerous nanometric fluid crystalline inclusions SiO2, CaCO3, KCl KAlSi3O8. integrated chemistry nanoinclusions suggests that was crystallized mixture two end- members, which includes carbon-rich hydrous-silicic Si, Al, K hydrous-saline rich Cl, K, Na. Traces carbonate, sulphate phosphate coupled presence metallic cations such as Fe, Mg, Ti, Cr, Co, Zn, Zr, Pb, As Hg found are coherent local geochemical diversity host metasedimentary rocks. oxidation state diamond-forming close C-CO buffer, for example, fO2 = )6 log units, is at upper limit stability region. dislocation arrays indicating low-angle grain boundaries together zig-zag features or kinks reflects rapid crystallization diamond. Triangular pockets steps surface {110} {111} planes could promote formation C-H C-OH bonds probably facilitate process graphitization. microstructural UHPM well their undisputed crustal ⁄ organic carbon can be used better understanding origin any both kimberlitic alluvial sources, including enigmatic black - commonly called carbonado.